The invention relates to a luminaire comprising:
concave, elongated reflectors which are arranged so as to be essentially opposite and parallel to each other, and which reflectors limit, with a longitudinal edge, a luminous window; PA1 means for accommodating an elongated electric lamp between the reflectors; PA1 a plurality of flat, light-scattering lamellae between the reflectors, transverse to the reflectors and transverse to the luminous window, which lamellae have an inner edge and a concave outer edge in the luminous window.
Such a luminaire is known from U.S. Pat. No. 5,758,954.
In the known luminaire, the inner edge of the lamellae is straight, so that, near the reflectors, the lamellae exhibit a greater height dimension, i.e. a larger distance from the inner edge to the outer edge, than centrally between the reflectors.
The reflectors do not only focus the light generated by a lamp accommodated in the luminaire but also screen the lamp in a direction transverse to the lamp, and in directions surrounding said direction, so that the lamp can only be observed through the longitudinal edges of the reflectors, see FIG. 2a, outside a selected angle .alpha. made with a plane Q. In the longitudinal direction of the lamp, and in directions surrounding said direction, the lamellae have a screening effect, so that, also in the longitudinal direction of the lamp, the lamp can only be observed outside an angle made with plane Q. In this manner, the reflectors and the lamellae preclude glare if the luminaire is observed at relatively large angles with the normal to plane Q. This screening effect is also necessary to prevent disturbing reflections, for example at display screens. Screening is efficient if there is a screening effect both in directions around the longitudinal direction of the lamp and in a direction transverse to the lamp at a substantially equal angle .alpha..
The above-mentioned document explains that for efficient screening, the lamellae must have a concave outer edge. In conventional lamellae, which do not only have a straight inner edge, but also a straight outer edge, screening in the longitudinal direction of the lamp is greater than in directions surrounding the longitudinal direction. If the screening effect in the longitudinal direction of the lamp is chosen to be equal to that in a direction transverse to the lamp, then the screening effect in directions around the longitudinal direction is too small and the standard for screening is not met in all directions. If this is precluded, for example by arranging the lamellae with a smaller interspace, then the screening effect in the central part of the lamellae is excessive, leading to a loss of light caused by additional reflections at the lamellae. This can be attributed to the fact that reflections are always accompanied by absorption.
The lamellae of the known luminaire may alternatively be three-dimensional bodies, for example folded from aluminium strip, which flare out from the outer edge to the inner edges. The inner edges of the lamellae may also be concave in order to preclude that, after reflection at the surfaces of the lamellae facing the lamp, bright images of the lamp are formed on the reflectors, which can be observed as disturbing bright spots from the angle .alpha. screened by the reflectors.
It is a drawback of the known luminaire having flat lamellae, that the lamellae cause undesirable reflections and unnecessary loss of light.
In DE-U-7613194 a description is given of a luminaire in which the flat lamellae have a largely convex outer edge and a largely concave inner edge. The known, above-described drawback of lamellae having a straight outer edge, i.e. inefficient or insufficient screening, applies to a greater extent to these lamellae.